The present invention relates to an improved structure for axially mounting a filament within an incandescent lamp.
The mounting of filaments within incandescent lamps may be accomplished in an axial or vertical manner, commonly termed CC8, or in a transverse or horizontal manner commonly termed CC6. The transverse mounting is beneficial with regard to the strength of the mounted filament, but the light output yielded by such transverse mounting is less than that obtainable from axial mounting. The axial mounting places the filament lengthwise or axially along the centerline of the lamp which is optically beneficial in providing approximately four (4) percent more light output relative to a transverse placement of the filament within the lamp.
The maximum spacing between the conductive members of both the axial and transverse mounting of the filament is limited by the diameter of the neck portion of the lamp in that both mounting structures are inserted into the confines of the lamp by way of the neck portion during the manufacturing process of the lamp. In an axially oriented filament, the maximum spacing between the filament and the conductive member of the mount which runs lengthwise of the filament, is determined by the desired position of the filament, relative to the lamp. From performance considerations, when the filament is positioned on the centerline of the lamp, this maximum spacing distance is about one-half (1/2) of the diameter of the neck portion.
One of the factors of this performance is related to the gas convection around the filament. When the filament is positioned on the centerline of the lamp, essentially and advantageous only a single hot-spot accurs at the top, central portion of the lamp. When the position of the filament is shifted off of the centerline, a hot spot is created at the top portion of the lamp, and also at the side of the lamps. Typically these hot-spots are suspected to contribute to degrading the life expectancy of the lamps making the centerlined positioning of the filament advantageous. Further, from aesthetic considerations in lamps having a clear or frosted outer envelope, the customer expects the filament to be positioned at the centerline of the lamp.
In axially oriented filaments, an arcing problem may commonly occur between the filament and the conductive member of the mounting structure that runs alongside the filament. This arcing problem is particularly noticeable in low wattage filaments having thin wire sizes in that the thin wire sizes are lacking in strength, and when subjected to bending and sagging actions, the filament may move away from its initial position and find its way to close proximity of the conductive member, thus allowing for an arcing condition to be created. It is desired that means be provided which reduces this possible arcing condition so that the axial oriented filament may be used in lamps to thereby maintain the benefits of the increased light output relative to transverse oriented filaments.
Accordingly it is an object of the present invention to provide means for reducing the arcing conditions, between the filament and the conductive member that runs alongside of the filament, typically experienced by filaments oriented in an axial manner within an incandescent lamp.